1. Field of the Invention
The present invention relates to a road surface undulation estimation device and a road surface undulation estimation method for estimating an undulation of a road surface on which a vehicle travels.
2. Description of the Related Art
In recent years, there have been increasingly proposed preventive security systems, which are configured to use sensors installed on a vehicle to detect objects in a periphery of the vehicle, thereby avoiding a danger in advance. In this system, the position of the object needs to be acquired highly precisely.
On this occasion, when a camera is used as a device for sensing the periphery of the vehicle, in order to highly precisely calculate the position of the object, it is important to accurately calibrate an installation state of an in-vehicle camera on the vehicle, namely, an installation angle of the in-vehicle camera with respect to a road surface.
In general, when the in-vehicle camera is calibrated before the shipment, at a location where the road surface is horizontal or the inclination of the road surface is constant, an installation angle of the in-vehicle camera with respect to the road surface is acquired in advance on the assumption that the road surface is a horizontal surface. During vehicle travel, an object on the road surface appearing in a camera image captured by the in-vehicle camera is detected, and a position of the object in the image is acquired. Then, the position of the object in the real space is acquired from the position of the object in the image based on the installation angle of the in-vehicle camera acquired in advance.
In the method described above, it is assumed that the installation angle of the in-vehicle camera acquired in advance and an installation angle of the in-vehicle camera with respect to a road surface on which the vehicle is travelling match each other. However, an undulation exists on the road surface on which the vehicle travels in the real environment, and thus the road surface is not always a horizontal surface. Further, depending on the travel location of the vehicle, the undulation of the road surface dynamically changes. Therefore, in practice, the installation angle of the in-vehicle camera acquired in advance and the installation angle of the in-vehicle camera with respect to the road surface on which the vehicle is travelling do not always match each other. Thus, if the position of the object in the real space is acquired on the above-mentioned assumption, there is a problem in that precision of detecting the position of the object may decrease.
Thus, the road surface on which the vehicle travels has the undulation in the real environment, and hence a technology for estimating the undulation of the road surface on which the vehicle travels is necessary. As an example of coping with the above-mentioned problem, there is proposed an in-vehicle camera automatic calibration device (for example, refer to Japanese Patent Application Laid-open No. 2013-238497) configured to calibrate the installation angle of the in-vehicle camera with respect to the road surface in real time during the travel of the vehicle with use of motion information on an object existing on the road surface, but the device is not configured to estimate the undulation of the road surface on which the vehicle travels.
As described above, the road surface on which the vehicle travels has the undulation in the real environment, and hence a technology for estimating the undulation of the road surface on which the vehicle travels is necessary.